Which of the following is the German translation for "plug"?

The German translation for "plug" is "Stecker." In German, "Stecker" specifically refers to the device that is plugged into a socket, facilitating the connection of electrical devices to a power supply. This word directly corresponds to how "plug" is used in English, making it the appropriate choice in this context.

The other terms—such as bolt, joint, and socket—have distinct meanings that do not align with the concept of a plug. A bolt refers to a type of fastener, a joint signifies a point of connection between two items, and a socket pertains to the receptacle that receives a plug. Understanding these definitions helps clarify why "Stecker" is the most fitting translation.